The patent DE 196 13 833 B4 discloses an internal gear pump having an annulus and a pinion which is arranged eccentrically in the annulus such that it meshes with the annulus. The pinion is arranged for conjoint rotation on a pump shaft which serves to drive the pinion in rotation. When driven in rotation, the pinion drives the annulus, with which said pinion meshes, in conjoint rotation, with the result that the internal gear pump is driven and delivers fluid in a manner known per se. The pinion is an externally toothed gearwheel and the annulus an internally toothed gearwheel, and they are known as pinion and annulus here for unambiguous designation and to distinguish between them.
At the circumference, the pinion and the annulus delimit toward the inside and toward the outside a crescent-shaped pump space between one another, said pump space being covered laterally by rotationally fixed axial disks which bear in a sealing manner against end sides of the pinion and of the annulus. The lateral sealing is not hermetically sealed, the axial disks bear in the manner of plain bearings against the end sides of the pinion and of the annulus, and limited leakage is acceptable. An optimum between low friction and low leakage should be found.
In the circumferential direction, the axial disks extend at least over a pressure region of the pump space. In the axial direction, the axial disks are pressurized on their outer sides that face away from the pinion and the annulus in what are known as pressure fields and as a result are urged into abutment against the end sides of the pinion and of the annulus. The pressure field is a usually shallow depression which extends approximately over the pump space or the pressure region of the pump space. Such axial disks are also known as pressure disks or control disks or as pressure plates or control plates. They are typically in the form of disks or plates, although this is not essential for the disclosure.
The pump shaft of the known internal gear pump is rotatably mounted on both sides of the pinion in shaft bearings. The shaft bearings are located outside the axial disks, i.e. the axial disks are located between the shaft bearings on one side and the pinion and the annulus on the other side of the axial disks.